1. Field of the Invention
This invention relates to a process for cospinning synthetic trilobal filaments differing in modification ratios. More particularly, the filaments are cospun from trilobal spinneret orifices of different configurations.
2. Description of the Prior Art
Synthetic filaments having trilobal cross-sections and particular benefits associated therewith are described, for example, in U.S. Pat. No. 2,939,201. A characteristic of such filaments is their cross-section modification ratio, or MR. Certain benefits can be obtained from mixtures of such filaments or fibers having different modification ratios as described, for example, in U.S. Pat. No. 3,220,173. A convenient method of preparing such filament mixtures is to co-spin the different types in the desired ratio and to process the combined filaments through subsequent steps such as drawing, crimping, cutting into staple, etc. as a single mixed-filament product.
When filaments of two different modification ratios are co-spun using two differently dimensioned sets of known capillaries such as those with three intersecting slots with each having parallel sides, random fluctuations in process variables such as spinning temperature cause MR changes along and among filaments. Process adjustments to maintain an acceptable difference in MR between the two filament species is quite difficult.
An object of this invention is to reduce the sensitivity to normal spinning process fluctuations of changes in the difference in modification ratios among filaments cospun from a common polymer supply through at least two spinning capillaries designed to yield different filament modification ratios and where one of the modification ratios is greater than 1.9.